Antioxidants for mineral oil lubricants and compositions containing the same



Patented June 13, 1950 ANTIOXIDANTS FOR MINERAL OIL LUBRI- CANTS ANDCOMPOSITIONS CONTAINING THE SAME Herschel G. Smith, Wallingford, andTroy L. Cantrell, Lansdowne, Pa., and John G. Peters, Audubon, N. 3.,assignors to Gulf Oil Corporation, Pittsburgh, Pa., a corporation ofPennsyl- Vania No Drawing.

Application December 21, 1948, SerialNo. 66,586

18 Claims. (Cl. 252-50) thermore, many lubricating oil compositions.

which may be highly satisfactory for the lubrication of other mechanismshave been found wholly unsuitable for use as turbine oils.

The formation of varnishes, gums and sludges on engine surfaces is dueat least in part to oxidation effects on mineral lubricating oils. Inturbine oils the problem of oxidation is further aggravated because innormal use turbine oils rapidly become contaminated with water.

It has heretofore been proposed to employ as oxidation inhibitorsdiamino diaryl alkanes, such as tetramethyland tetraethyldiaminodiphenyl methane. However, the antioxidant potency of such compounds hasnot been entirely satisfactory because it is relatively low.

It is an object of this invention, therefore, to provide an additionagent for mineral oil lubricants which will inhibit the oxidativedeterioration of such lubricants.

It is a further object of this invention to provide improved mineral oillubricant compositions which are remarkably stable against oxidationunder service conditions.

These and other objects are accomplished by the present inventionwherein an addition agent for mineral oil lubricants is prepared bycondensing an N-diethyltoluidine and formaldehyde in the presence of anactivated clay catalyst, and recovering the condensation product. Thecondensation product so obtained is a light-colored product which, whenadded to mineral oil lubricants, confers a remarkable stability againstdeterioration by oxidation. Such condensation products and the mineraloil lubricant compositions containing them are believed to be novel andare considered parts of our invention. Contrary to what may be expectedfrom the nature of the reactants, we do not obtain highly-condensed,insoluble resinous products. On the contrary, when the above reactantsare condensed in accordance with our invention, there are btainedlight-colored condensation products which are non-resinous and which arereadily soluble in mineral oils.

Any of the isomeric N-diethyltoluidines, that is, the ortho, meta andpara N-diethyltoluidines, or mixtures thereof, may be employed inaccordance with our invention.

In performing the condensatiomthe reactants are mixed and heated to amaximum temperature of 350 F. We have found that if the temperature of350 F. is exceeded to any substantial extent, the condensation productformed tends to be resinous and insoluble. The preferred tem peraturefor the condensation ranges from The proportions of the reactants varyas follows. For each mol of the N-diethyltoluidine, there is employedfrom 0.5 to 1 mol of formaldehyde. Ordinarily, it is preferred to usefrom 5 to 10 per cent by weight of the activated clay catalyst, based onthe total weight of the reactants. However, smaller amounts, as low as 1per cent by weight, and larger amounts, as high as 20 per cent byweight, may also be employed; but larger amounts than about 10 per centby weight are ordinarily not necessary.

In lieu of formaldehyde, any formaldehydeyielding compound, such asparaformaldehyde, dioxymethylene and trioxymethylene may be employed. Insuch case, the amount of formaldehyde-yielding compound used is based onthe equivalent number of mols of formaldehyde yielded within the rangeof proportions of formaldehyde set forth hereinabove. Accordingly, asused in the appended claims, the term "formaldehyde is intended toinclude formaldehyde-yielding compounds as well as formaldehyde itself.

Various activated clays may be employed in accordance with ourinvention. Such materials are well known in the art and comprise anatural clay, such as bentonite, fullers earth, floridin and smectite,which has been acid treated in order to activate the clay. Thesematerials are described in U. S. Patent 1,898,165, for example.

In preparing our new addition agents, the reactants and catalyst areplaced into a reaction vessel which is then closed and the mixtureheated with agitation until all of the formaldehyde orformaldehyde-yielding compound has been consumed. At this time, thewater which is formed as a result of the condensation is removed,preferably under vacuum, and the dehydrated condensation product is thenfiltered to remove the activated clay catalyst. In some instances, it isdesirable to prepare our new addi- 3 tion agent in a concentrate in amineral lubricating oil which may then be diluted with additional oil tothe concentration desired in the final lubricating composition. In suchinstances, the mineral lubricating oil may be added in a suitableamount, say in a weight equal to the weight of reactants, to thereaction mixture in the reaction vessel, and the condensation productobtained will then be a concentrated solution of the addition agent inthe mineral lubricating oil.

The condensation products obtained in accordance with out invention areliquids or crystalline solids. While the exact nature of the chemicalcomposition of the condensation products is unknown, the reactants enterinto a unitary product. The exact manner in which the catalystinfluences the reaction is unknown. However, regardless of any theoryinvolved, the use of an activated clay catalyst is an essential featureof our invention, since if the catalyst is omitted, black, insoluble,resinous condensation products may be obtained.

The following examples illustrate the preparation of our new additionagent.

Example I.--Into an iron reaction vessel, equipped with means foragitation and a reflux condenser, therewere placed 2 mols ofN-diethylm-toluidine, 1 mol of formaldehyde in a 37 per cent by weightaqueous solution, and 10 per cent by weight of the reactants of Filtrol(an activated montmorillonite) as a catalyst. The mixture was agitatedand refluxed at 210 F. for 10 hours, and then all water, both that addedwith the formaldehyde and formed in the reaction, was distilled off byheating at 280 F. and the product dried. The product was then filteredthrough Celite, a diatomaceous earth filter aid. The product had thefollowing properties:

Gravity, A. P. I. 11.4 Color, N. P. A. 3.75 Neutralization No. 0.36

Example II.,An addition agent was prepared by reacting 6 mols ofN-diethyl-m-toluidine and mols of formaldehyde in the presence of 10 percent by weight of the total reactants of an acti: vated montmorillonitecatalyst (Filtrol) under the conditions set forth in Example I. Theproduct had the following properties:

Gravit, A. P. I. 10.8 Color, N. P. A. 4.0 Neutralization No. 0.45

Example III.An addition agent was prepared by reacting 3 mols ofN-diethyl-m-toluidine and 2 mols of formaldehyde in the presence of 5per cent by weight of the total reactants of an activated clay(montmorillonite) catalyst under the the conditions set forth in ExampleI. The product had the following properties:

Gravity, A. P. I 9.9 Color, N. P. A 5.0 Neutralization No. 1.2

eral oil lubricant composition. As stated, our new addition agents areremarkably effective in inhibiting the oxidative deterioration ofmineral oil lubricant compositions For this purpose small amounts of ournew addition agents are generally sufllcient. For example, our additionagents may be added to mineral lubricating oils in minor amounts, sayfrom 0.001 to l per cent by weight on the mineral oil, sufficient toinhibit the oxidative deterioration of the oil. Larger amounts of ournew addition agents may be used if desired but it is ordinarilyunnecessary to do The following examples illustrate the remarkableantioxidant eflects of our new addition agents. In the followingexamples, the base oil and the same oil blended with our new additionagents are subjected to a standard oxidation test which measures thestability of the oils to oxidation. The oxidation test referred to is astandard test designated A. S. T. M. D943-47T. Briefly, the testcomprises subjecting the oil sample .to oxygen at a temperature of C.(203 F.)

in the presence of water and an iron-copper catalyst, and determiningthe time required to build up a neutralization number of 2. The flow ofoxygen is maintained at 3 liters per hour. The remarkably effectivestability to oxidation of mineral oil lubricant compositions containingour new addition agents is illustrated by the results shown in thefollowing examples.

Example IV.An improved steam turbine oil was prepared by adding 0.5 percent by weight of the addition agent prepared in accordance with ExampleI to a turbine oil base. A comparlson of the base oil and the base oilblended with the antioxidant showed the following resuits:

Base Improved Oil Oil Gravity, API 28. 6 28. 5 Oxidation Test AS'IMD94347T 203 F., 3 L.

Oxygen per Hr.

Time Oxidized, Hrs 180 3,350 Neutralization No 2. 0 2. 0

Example V.To a refined motor oil base, there was added 0.5 per cent byweight of the addition agent prepared in accordance with Example III. Acomparison of the base oil and improved oil follows:

Base Improved Oil Oil Gravity, API 27. 8 27.7 Viscosity, SUV: F 248 246Color, NPA 3.0 3.0 Neutralization No 0. 01 0. 02 Oxidation Test, ASTMD043-47T 203 F., 3 L.

Oxygen per Ha:

Time Oxidized, Hrs l9 3, 506 Neutralization No 2. 0 2. 0

The above examples show the'remarkable oxidation stability imparted tomineral oil lubricant compositions by the use of our new additionMineral oil lubricant compositions conants. Thus, condensation productsprepared from other functionally similar compounds have been found tobeeither prooxidant or to show no antioxidant effects whatsoever. Forexample, we have prepared condensation products similar to our newaddition agent by substituting aryl amines such as toluidine, xylidine,or N-diethylaniline for the N-diethyltoluidine. The resultingcondensation products were found to be entirely unsuitable forinhibiting the oxidative deterioration of mineral oil lubricantcompositions.

As has been shown in our copending application Serial No. 66,585, filedof even date herewith, which describes and claims the condensation ofN-dimethylaniline and formaldehyde to produce excellent antioxidants formineral lubricating oils, the type of amine used to condense with g theformaldehyde is highly critical and can only be determined byexperiment. This is particularly apparent in the instant applicationwhen it is considered that a condensation product of N- diethylanilineand formaldehyde (prepared exactly as the condensation product ofN-diethyltoluidine and formaldehyde of this invention) fails to improvethe oxidation stability of a mineral lubricating oil when added theretoin an amount of 0.5 per cent; whereas, the use of N- diethyltoluidine, ahomologue of N-diethylaniline, yields excellent antioxidants. We havealso found that mixtures of N-diethyltoluidine and N-dimethylaniline maybe condensed with formaldehyde to produce excellent antioxidants. Thisis described and claimed in our copending application Serial No. 66,587,filed of even date herewith. Although N-diethylaniline when condensedalone with formaldehyde does not yield a satisfactory antioxidant, whenmixtures of N- diethylaniline and N-dimethylaniline are condensed withformaldehyde in the presence of an activated clay, good antioxidants areobtained. This is described and claimed in our copending applicationSerial No. 66,588, filed of even date herewith.

While we have shown in the examples the preparation of compoundedlubricating oils, our invention is not limited thereto but comprises allmineral oil lubricant compositions containing our new addition agents,such as greases and the like. If desired, other known addition agentsmay be incorporated into the lubricant compositions prepared inaccordance with our invention. For example, pour point depressants,extremepressure agents, viscosity index improvers and the like may beadded.

Resort may be had to such modifications and variations as fall withinthe spirit of the invention and the scope of the appended claims.

We claim:

1. The process of preparing an addition agent to 10 per cent by weighton the total reactants of an activated clay catalyst at a temperature offrom 150 to 300 F. to condense together the reactants, and recoveringthe condensation product.

3. The process of preparing an addition agent for mineral oil lubricantswhich comprises adding an activated clay catalyst, 1 mol of anN-diethyltoluidine and from 0.5 to 1 mol of formaldehyde to a minerallubricating oil, heating the mixture to a temperature not in excess of350 F. to form a condensation product, and recovering a solution of thecondensation product in the mineral lubricating oil.

4. The process of preparing an addition agent for mineral oil lubricantswhich comprises heating 2 mols of N-diethyl-m-toluidine and 1 mol offormaldehyde in the presence of about 5 to 10 per cent by weight on thetotal reactants of an activated clay catalyst at a temperature of fromto 300 F. to condense together the reactants, and recovering thecondensation product.

5. The process of preparing an addition agent for mineral oil lubricantswhich comprises heating 6 mols of N-diethyl-m-toluidine and 5 mols offormaldehyde in the presence of about 5 to 10 per cent by weight on thetotal reactants of an activated clay catalyst at a temperature of from150 to 300 F. to condense together the reactants, and recovering thecondensation product.

6. The process of preparing an addition agent for mineral oil lubricantswhich comprises heating 3 mols of N-diethyl-m-toluidine and 2 mols offormaldehyde in the presence of about 5 to 10 per cent by weight on thetotal reactants of an activated clay catalyst at a temperature of from150 to 300 F. to condense together the reactants, and recovering thecondensation product.

7. A non-resinous condensation product of 1 mol of an N-diethyltoluidinewith from 0.5 to 1 mol of formaldehyde, said product being obtained bythe process of claim 1.

8. A non-resinous condensation product of 2 mols ofN-diethyl-m-toluidine and 1 mol of formaldehyde, said product beingobtained by the process of claim 4.

9. A non-resinous condensation product of 6 mols ofN-diethyl-m-toluidine and 5 mols of formaldehyde, said product beingobtained by the process of claim 5.

10. A non-resinous condensation product of 3 mols ofN-diethyl-m-toluidine and 2 mols of formaldehyde, said product beingobtained by the process of claim 6.

11. A lubricant composition comprising a major amount of a minerallubricating oil, and a minor amount, suflicient to inhibit the oxidativedeterioration of said oil of a non-resinous condensation product of onemol of an N-diethyltoluidine with from 0.5 to 1 mol of formaldehyde,said product being obtained by the process of claim 1.

12. A lubricant composition comprising a major amount of a minerallubricating oil, and a minor amount, from 0.001 to 1.0 per cent byweight of said oil, of a non-resinous condensation product of anN-diethyltoluidine with from 0.5 to 1 mol of formaldehyde, said productbeing obtained by the process of claim 1.

13. A lubricant composition comprising a major amount of a minerallubricating oil, and a minor amount, suflicient to inhibit the oxidativedeterioration of said oil of a non-resinous condensation product of 2mols of N-diethyl-m-toluidine and 1 mol of formaldehyde, said productbeing obtained by the process of claim 4.

14. A lubricant composition comprising a major amount of a minerallubricating oil, and a minor amount, sufficient to inhibit the oxidativedeterioration of said oil of a non-resinous condensation product of 6mols of N-diethyl-m-toluidine 15. A lubricant composition comprising amajor 1 amount of a mineral lubricating oil, and a minor amount,suflicient to inhibit the oxidative deterioration of said oil of anon-resinous condensation product of 3 mole of N-diethyl-m-toluidine and2 mol of formaldehyde, said product being obtained by the process ofclaim 6.

16. The composition of claim 13, wherein the condensation product ispresent in an amount of 0.5 per cent by weight,

1'7. The composition of claim 14, wherein the condensation product ispresent in an amount of 0.5 per cent by weight.

18. The composition of claim 15, wherein the condensation product ispresent in an amount of 0.5 per cent by weight.

HERSCHEL G. SMITH. TROY L. CAN'IRELL. JOHN G. PETERS.

. a I REFERENCES CITED The following references are of record in thefile of this patent:

UNITED STATES PATENTS Number Name Date 1,584,473 Regal May 11, 19261,803,331 Kladivko May 5, 1931 1,873,799 Vacher Aug. 23, 1932 1,954,484Mattison Apr. 10, 1934 2,223,411 Fuller et al. Dec. 3, 1940 FOREIGNPATENTS Number Country Date 12,021 Australia Feb. 29, 1928

1. THE PROCESS OF PREPARING AN ADDITION AGENT FOR MINERAL OIL LUBRICANTSWHICH COMPRISES HEATING 1 MOL OF AN N-DIETHYLTOLUIDINE WITH FROM 0.5 TO1 MOL OF FORMALDEHYDE IN THE PRESENCE OF AN ACTIVATED CLAY CATALYST AT ATEMPERATURE NOT IN EXCESS OF 350*F. TO CONDENSE TOGEHER THE REACTANTS,AND RECOVERING THE CONDENSATION PROD-UCT.
 12. A LUBRICANT COMPOSITIONCOMPRISING A MAJOR AMOUNT OF A MINERAL LUBRICATING OIL, AND A MINORAMOUNT, FROM 0.001 TO 1.0 PER CENT BY WEIGHT OF SAID OIL, OF ANON-RESINOIUS CONDENSATION PRODUCT OF A N-DIETHYLTOLUIDINE WITH FROM 0.5TO 1 MOL OF FORMALDEHYDE, SAID PRODUCT BEING OBTAINED BY THE PROCESS OFCLAIM 1.